Control device for hydraulic presses



.April 28, 1953 o. c. G. WENNBERG 2,636,433

y CONTROL DEVICE FOR HYDRAULIC PRESSES Filed April 29, 1949 PatentedApr. 28, 1953 CONTROL DEVICE FOR l HYDRAULIC PRESSES'- i Olov CarlGustav Wennberg, Karlstad, Sweden, assignor to Svenska, FlygmotorAktiebolaget, Trollhattan, Sweden, a corporation of Sweden :ApplicationApril 29, 1949, serial No. 90,363 I In Sweden March 13, 1946 2 Claims.(C1. 10U-48) s 1 The present invention relates to platens for hydraulicpresses, particularly presses of the type operating at a high pressureand requiring a great accuracy as to the correct engagement betweenl theusually large press platens, a stationary one and a movable one, and thearticlev to be pressed therebetween. More specifically the invention maybe adapted to presses for stamping matrices.

The movable press platen can be caused to press in an oblique position,i. e. a position in which it is not parallel with the stationary platen,for example, by an article of any kind being located at the margin ofthe platen, whereby in case of high pressures the accuracy of the press--ing operation can be entirely jeopardized, if there is no protectionagainst the consequence of the nonuniiorm pressing. An object of theinvention is to provide means, by which said disadvantages may beavoided and by which a correct self-adjustment of the movable platenrelatively to the stationary one can be obtained.

A further object of the invention is to provide means, by which thepressing operation may be immediately interrupted at an initiation to anoblique position of the movable platen as a consequence of an unevenload, whereby the platen is prevented from pressing in an obliqueposition.

A still further object of the invention is to provide means permittinguniversal adjustment of the movable press platen relatively to the pressplunger and to provide spring means of such a nature as to tend to keepthe platen in a position correct for the pressing operation.

The 'invention will be more particularly described hereinafter andillustrated by way of example in the accompanying drawing in which:

Fig. 1 is a front elevation of the press, the lower parts being shown ina vertical section, and

Fig. 2 is a horizontal section along the line II-II in Fig. l andillustrates a top view of the movable platen.

In the drawing, I designates the press platen mounted stationary in theframe of the press, 2 being the movable platen having a sphericalbearing 3 seated and universally movable in a corresponding sphericalseat 4 in the press plunger 5, which is vertically reciprocable in thepress cylinder or frame B. A pressure conduit 1 extends from a pump suchas a screw pump or gear pump 'la driven by an electric motor 1b to thepress chamber 8, a packing 9 being conventionally mounted between thewalls of the chamber 8 and the plunger 5. An outlet branch 'lccomprising an operating valve 'Id extends from the conduit 1, and thepump has an inlet pipe 1e. Four helical springs I I-are mounted betweenthe platen 2,

which is square in the present case, and a correspondingly squareportion I0 made integral with the press plunger 5. yThe springs arelocated in theproximity of the corners of the platenas shown in thedrawing, i. e. at a considerable dis-5 tance from the centre of thetable, whereby the springs are made very sensibly responsive to apossible movement of the platen to an oblique position, i. e. todeviations of the platens from their correct parallel position. Eachspring I I is seated in recesses I Ia, I Ib in the platen 2 and in theportion I0 projecting from the press plunger. Each spring II is mountedon a bolt I2 having a head I3 engaging the top of a ring I4, which formsan upper support for the spring, the lower end of which is seated on ashoulder I5 in the bottom of the recess I Ib. Screwed up on the lowerscrew-threaded end of the bolt I2 to engagement with the bottom of theportion I0 are nuts I6 by which the prestrain of the spring, asmentioned above, may be adjusted. Below each bolt I2 is a switch I'Isupported by the cylinder 6 or frame and coupled in the circuit ofoperation of the press. There are four switches Il (indicated by blockdiagrams in Fig. 1) coupled in series by leads I8, I9 the former ofwhich is connected to one terminal 2li of the motor 'Ib and the latterto one terminal of a source of current 2|, a further lead 22 connectingthe other motor terminal 23 to the other terminal of the source ofcurrent 2 I. The switch has an operating portion 24 adapted to beactuated by the bolt and being located in alignment therewith in theproximity of the end thereof.

In operation the pump 'Ia delivers pressure me-f dium such as oil toconduit 'I and chamber 8, valve ld being closed. The plunger 5 rises andmoves the press platen 2 toward the press platen I, thereby compressingthe work. Should the press platen 2 tilt, one or more of the bolts I2will be displaced, and as a result the corresponding switch or switchesare actuated to cause an interruption of the circuit controlling motor1b. After such circuit interruption and following the stop of thepressing operation the press chamber 8 is emptied from pressure liquidby opening valve ld, whereupon the springs II will be able to restorethe platen 2 to a position which is correct for the future pressingoperation.

The detailed construction of the device may of course be changed withoutdeparting from the principles of the invention.

What I claim is:

1. A control device for a hydraulic press comprising a press plunger, apress platen cooperating with the plunger to contact centrally with theplunger. said plunger and platen having a central spherical bearingwhereby the plunger and platen Vwill have relative tilting movement, aplurality of switches-1t` arranged rxoncentrallyifrelativetoA the pressplunger land platen, means tos'upplyhydraulic pressure fluid to theplunger which is in to said means to thereby interrupt the flow ofpressure fluid to the plunger; and. anboltfsur-' f rounded by apre-strained springoreaclz-'switchf with the bolt contacting thepressfpl'ateriant'the` switch, said spring being interposedlbetween-the:

platen and plunger. Y v

2. A control device for a hydraulic press com,- prising .a pressplunger, a press platen cooperating with the plunger to contactcentrally with the plunger; said Vplunger and' yplatenhavinga een trai'spherical bearing whereby Vthe"plunger-and platen will 'haverelative-tilting movement, a plurality ofswitches arranged nonecentrallyrelatveto the press plunger and platen, means'to supply hydraulicpressure -fluid to the plunger which is in electrical connection withthe switches so that when the press platen tilts relative to the plungerone of the switches will be operative relative to said means to therebyinterrupt ,.theiflowf of pressure-fluidf'tof the plunger, and a. boltsurrounded by a ,spring for' each switch with the spring pre-strainedbetween the press platen and the plunger, the bolt being interposedbetweenatheswitch and the platen, said plunger being substantiallyrectangular with a switch provided in each corner.

` OLOV CARE GUSTAV WENNBERG.

RefrenccsfCited-'in the le of this patent UNITED STATES PATENTS NumberName Date 610,524: Cleveland Sept. 13, 1898 1,932,556 Meranda Oct. 31,1933 Y 2,309,944- Flowers Feb.. 2, ,1943 2,343,167 .Bench -Feb 29,19%l

FORFHGNTPATENTS Number Country Date 253,735' Germany; Nov.' 15,1912

